AP Biology Unit 8 - Ecology Notes

Responses to the Environment:

  • Allelopathy: Plants produce chemicals preventing the growth of neighboring plants.
  • Cross-pollination: Pollination involving pollen from another flower or plant.
  • Offspring: A new organism resulting from reproduction.
  • Calvin Cycle: Light-independent reactions of photosynthesis where ATP and NADPH are used to build sugars.
  • Krebs Cycle (Citric Acid Cycle): Second stage of cellular respiration where pyruvic acid is broken down into carbon dioxide.
  • Phototaxis: Movement in response to light.
  • Abiotic: Non-living components of the environment.
  • Biotic: Living components of the environment.

Energy Flow Through Ecosystems:

  • Producer: An organism that can produce its own food (autotroph).
  • Consumer: An organism that obtains food by consuming other organisms (heterotroph).
  • Decomposer: An organism that breaks down dead materials and waste.
  • Food web: Interconnected food chains showing energy flow in an ecosystem.
  • Food chain: Linear flow of energy between organisms (prey → predator).
    • Herbivore: Consumes only plant material (primary consumers).
    • Carnivore: Consumes only animal material.
    • Omnivore: Consumes both plant and animal material.
  • Energy flow: The flow of energy from the Sun to producers to consumers.
    • Approximately 10% of energy is transferred to the next trophic level.
    • Primary consumer: Eats producers.
    • Secondary consumer: Eats primary consumers.
  • Other Vocabulary
    • Detritivores: Consume dead organic matter.
    • Autotroph: Produces own food from the sun.
    • Heterotroph: Obtains food by consuming other organisms.
    • Chemotroph: Obtains energy from chemicals.

Population Ecology:

  • Population: Organisms of the same species living in a specific area.
  • Age structure: Distribution of a population by age groups (cohorts).
  • Population density: Number of individuals per unit area.
  • Exponential growth: Population growth with unlimited resources, resulting in a J-shaped curve.
  • Carrying capacity: Maximum number of individuals an ecosystem can support.
    • Acts as a limiting factor for exponential growth.
  • Density-dependent factor: A factor whose effect on a population depends on population density.
  • Density-independent factor: A factor that affects a population regardless of its density.
  • Limiting factor: Any biotic or abiotic factor that restricts population size, distribution, or reproduction.
  • Logistic growth: Population growth considering carrying capacity resulting in an S-shaped curve.
  • K-selected species: Species with long lifespans that invest heavily in offspring (few, large offspring) and exhibit iteroparity, often following logistical growth patterns.
    • Iteroparity: Adults reproduce multiple times over their lifespan.
  • R-selected species: Species with short lifespans that produce many offspring (small, numerous offspring) and exhibit semelparity, often following exponential growth patterns.
    • Semelparity: Organisms reproduce in a single event during their lifetime.
  • Life history pattern: Traits related to growth, survival, and reproduction such as age-specific mortality, lifespan, age at first reproduction, and number of breeding events.
  • Survivorship curve: A graph showing the decline in the number of individuals in a cohort over time.

Community Ecology:

  • Community: Multiple species interacting in a single area.
  • Interspecific Interactions: Interactions between different species including competition, predation, herbivory, and symbiosis.
    • Competition: Occurs when resources are limited, and organisms compete for access.
    • Symbiosis: Relationships between interdependent organisms of different species.
      • Mutualism: Both species benefit.
      • Commensalism: One species benefits, the other is unaffected.
      • Parasitism: One species benefits (parasite), the other is harmed (host).
        • Parasite: Organism that uses the nutrients of another organism to survive.
    • Predation: One organism (predator) catches and consumes another (prey).
    • Interspecific Competition: Competition between different species for limited resources.
  • Competitive Exclusion: One species outcompetes another for limited resources, leading to the elimination of the less efficient species.
  • Ecological Niche: How a species utilizes the biotic and abiotic aspects of its environment.
    • Fundamental Niche: The potential range of resources a species can use without competition or limiting factors.
    • Realized Niche: The actual range of resources a species uses, considering competition and limiting factors.
  • Keystone Species: A species crucial to the structure and function of an ecosystem.
  • Invasive Species: Organisms that migrate to new locations, outcompete native species, and disrupt ecosystems.
  • Primary Succession: Ecological succession in an area where no previous biotic community existed.
  • Secondary Succession: Succession following a disturbance that does not destroy the soil.

Biodiversity:

  • Biodiversity: Variety of living organisms in an ecosystem, region, or the world.
  • Species: A group of organisms whose members are similar to each other in shape (morphology), physiology, biochemistry and behavior, and can interbreed to produce fertile offspring.
  • Habitat: The place where an organism or population lives.
  • Community: All living organisms in one habitat at one time
  • Population: All organisms of one species in one place and at one time
  • Species biodiversity: Differences between different species
  • Habitat biodiversity: The range of habitats organisms live in
  • Genetic biodiversity: Biodiversity within one species

Disruptions to Ecosystems:

  • Disturbance: An event that disrupts a biological community or ecosystem.
    • Can be natural or man-made.
    • Nonequilibrium Model: Communities are constantly changing due to disturbances.
    • Intermediate Disturbance Hypothesis: Moderate disturbance can result in greater diversity.
  • Ecological Succession: Changes in species composition after a disturbance, often increasing biodiversity.
  • Endangered Species: Species at risk of extinction.
  • Threatened Species: Species likely to become endangered.
  • Introduced Species: Species brought to a new area by humans (intentionally or unintentionally); also called non-native or exotic species.